The present application relates to force sensors and, more particularly, to piezo-electric force sensors for electromechanical brake systems.
Electromechanical brake systems have been developed for use in the automotive, aerospace and aeronautical industries to control the speed, stability and operation of various vehicles and devices. Electromechanical brake systems may be used in combination with, or in place of, conventional hydraulic brake systems.
A typical electromechanical brake system may include an electric motor adapted to advance a piston into engagement with one or more brake pads and/or a rotor, thereby generating a braking force. The applied braking force may be controlled by controlling the rotational power supplied by the electric motor in response to measurements of the braking force.
Various techniques have been developed for estimating and/or measuring the braking force. For example, the braking force may be estimated by monitoring the displacement of the piston and converting the displacement into a force signal by modeling the electromechanical brake system as a spring and multiplying the piston displacement by a spring constant. Alternatively, the braking force may be measured directly using a force gauge.
Force gauges may include piezo-electric materials adapted to generate a voltage signal (or other electrical signal) when subjected to a mechanical force or strain. The voltage signal may be correlated into a force signal. However, piezo-electric materials do not output a constant voltage when subjected to a constant force and therefore may give rise to inaccurate measurements of force.
Accordingly, there is a need for an improved piezo-electric force sensor and, in particular, an improved piezo-electric force sensor for measuring the braking force generated by an electromechanical brake system.